Elia G, De Marco A, Rossi A, Santoro M G
Institute of Experimental Medicine, Consiglio Nazionale delle Ricerche, Viale K. Marx, 15/43, 00137 Rome, Italy.
J Biol Chem. 1996 Jul 5;271(27):16111-8. doi: 10.1074/jbc.271.27.16111.
Heat shock proteins (HSPs) are induced in mammalian cells in a variety of pathophysiological states and have an important role in cytoprotection in vitro and in vivo. In this study, we report that the calcium ionophore A23187, a glucose-regulated protein (GRP) inducer, dramatically inhibits HSP70 synthesis and HSP70 mRNA transcription after induction by heat shock, sodium arsenite, or prostaglandin A1 treatment in human K562 cells. A23187 does not suppress, and it actually prolongs, the DNA-binding activity of the human heat shock transcription factor (HSF), while it alters HSF1 phosphorylation in heat shock-treated cells. To inhibit HSP70 expression, A23187 needs to be present during heat shock, while treatment before or after heat shock does not affect HSP70 mRNA transcription. The GRP inducer thapsigargin, which specifically inhibits the endoplasmic reticulum Ca2+-ATPase, has no effect on heat-induced HSP70 synthesis, indicating that A23187 inhibitory activity is not due to depletion of intracellular calcium stores and is independent of the concomitant induction of GRP genes. Inhibition of HSP70 expression is correlated with alterations in HSF1 phosphorylation in heat-shocked cells, but not in sodium arsenite-treated cells, indicating that different mechanisms may be involved in mediating A23187 inhibitory activity.
热休克蛋白（HSPs）在多种病理生理状态下的哺乳动物细胞中被诱导产生，并且在体外和体内的细胞保护中发挥重要作用。在本研究中，我们报告钙离子载体A23187（一种葡萄糖调节蛋白（GRP）诱导剂）在人K562细胞经热休克、亚砷酸钠或前列腺素A1处理诱导后，显著抑制HSP70的合成和HSP70 mRNA转录。A23187并不抑制，实际上还延长了人热休克转录因子（HSF）的DNA结合活性，同时它改变了热休克处理细胞中HSF1的磷酸化。为了抑制HSP70表达，A23187需要在热休克期间存在，而在热休克之前或之后处理并不影响HSP70 mRNA转录。GRP诱导剂毒胡萝卜素特异性抑制内质网Ca2 + -ATP酶，对热诱导的HSP70合成没有影响，表明A23187的抑制活性不是由于细胞内钙库的耗竭，并且独立于GRP基因的伴随诱导。HSP70表达的抑制与热休克细胞中HSF1磷酸化的改变相关，但与亚砷酸钠处理的细胞无关，表明可能涉及不同的机制来介导A23187的抑制活性。
